Why Do Doctors Calculate the End-Diastolic Volume?

Left ventricular end-diastolic volume is the amount of blood in the heart’s left ventricle just before the heart contracts. While the right ventricle also has an end-diastolic volume, it’s the value for the left ventricle, and how it relates to stroke volume, that serves as an important measurement for how well the heart is working.

The heart is made up of four chambers. The right atrium connects to the right ventricle and moves blood from the body to the lungs for oxygenation. Then the blood from the lungs returns to the heart via the left atrium. The blood then goes into the left ventricle, where it’s squeezed out of the heart to deliver oxygenated blood through the body.

When the heart’s ventricles squeeze to move blood forward, this is known as systole. Diastole, on the other hand, is when the ventricles relax and fill with blood. Blood pressure is a measurement of the pressures on the left side of the heart during both systole and diastole. If the heart is working effectively, it moves much of the blood in its ventricles forward when it squeezes. In this case, when the ventricles relax, not a lot of blood is left in the heart.

Left ventricular end-diastolic volume is often considered to be the same as preload. This is the amount of blood the veins return to the heart before contraction. Because there is no true test for preload, doctors may calculate left-side end-diastolic volume as a way to estimate preload.

Doctors use end-diastolic volume plus end-systolic volume to determine a measurement known as stroke volume. Stroke volume is the amount of blood pumped from the left ventricle with each heartbeat.

The calculation for stroke volume is:

stroke volume = end-diastolic volume – end-systolic volume

For an average-sized man, the end-diastolic volume is 120 milliliters of blood and the end-systolic volume is 50 milliliters of blood. This means the average stroke volume for a healthy male is usually about 70 milliliters of blood per beat.

Total blood volume also affects this number. The body’s total blood volume varies depending on a person’s size, weight, and muscle mass. For these reasons, adult women tend to have a smaller total blood volume, which results in a slightly lower end-diastolic and end-systolic volume compared to adult men.

A person’s end-diastolic volume tends to decrease with age.

A doctor can calculate these volumes through a few diagnostic tests, such as the following:

Left-heart catheterization. A catheter is threaded through a blood vessel and into the heart, allowing a doctor to perform different procedures to diagnose a heart problem.

Transthoracic echocardiogram (TTE). Sound waves create images of your heart through a device called a transducer.

Information from these tests can provide an understanding of how well the heart is working.

Stroke volume is part of another calculation of heart function known as cardiac output, or how much blood the heart is pumping out each minute. Cardiac output is calculated by multiplying the heart rate and the stroke volume.

The workings of end-diastolic volume are also described by a law known as the Frank-Starling mechanism: The more the heart muscle fibers are stretched, the harder the heart will squeeze. The heart can compensate for quite some time by squeezing harder. However, squeezing harder can cause the heart muscle to thicken over time. Ultimately, if the heart muscle gets too thick, the muscle can no longer squeeze as well.

There are a number of conditions related to the heart that can cause increases or decreases in end-diastolic volume.

An overly stretched heart muscle, known as dilated cardiomyopathy, can affect a person’s end-diastolic volume. This condition is often the result of a heart attack. The damaged heart muscle can become larger and floppy, unable to properly pump blood, which can lead to heart failure. As the ventricle enlarges more, the end-diastolic volume goes up. Not all people with heart failure will have a higher-than-normal end-diastolic volume, but many will.

Another heart condition that changes end-diastolic volume is cardiac hypertrophy. This often occurs as a result of untreated high blood pressure. In this case, the chambers of the heart become thicker, having to work harder against high blood pressure. At first, the end-diastolic volume decreases because the thicker heart muscle squeezes more strongly. Eventually, the heart muscle can’t get any thicker, and it starts to wear out. This causes the end-diastolic volume to increase as heart failure develops.

Sometimes abnormalities of the heart’s valves can affect the end-diastolic volume. For example, if the aortic valve that controls blood flow from the left ventricle to the aorta (the large artery that pumps oxygenated blood to the body) is smaller than normal, the heart can’t move blood out of the heart as well. This can leave behind extra blood in the heart in diastole.

Another example is mitral regurgitation, in which the blood doesn’t flow as well to the left ventricle. This can be caused by mitral valve prolapse, a condition that occurs when the mitral valve flaps don’t close properly.

Left ventricular end-diastolic volume is one of several calculations that doctors use to determine how well the heart is pumping. This calculation, combined with other information, such as the end-systolic volume, can tell your doctor more about your overall heart health.